Scientists are trying to create a contraceptive that stops sperm in its tracks

Boston University and Mapp Biopharmaceutical are leading a project to develop an antibody-based contraceptive. Adobe

Scientists are trying to create a new kind of contraception with a novel tactic: tangling up sperm so they can’t reach an egg.

The project relies on the precision targeting ability of monoclonal antibodies, which are widely used as drugs to treat everything from cancer to Crohn’s disease. Boston University and Mapp Biopharmaceutical, a San Diego-based drug company that specializes in this technology, are spearheading the research, and scientists across the country have signed on to help study the idea.

They’ve already scored early support: The National Institute of Child Health and Human Development recently awarded the team an $8 million grant.

advertisement

“There’s a real need for nonhormonal contraception. Not because the ones we have currently aren’t highly effective or safe, but the side effects can keep people from using them,” said Dr. Philip Darney, who studies contraception at the Bixby Center for Reproductive Health at the University of California, San Francisco. Those side effects can include irregular bleeding, headaches, and nausea.

But monoclonal antibodies are expensive drugs, which has raised some concerns that they will be unaffordable for many people who need better contraceptives, especially in developing countries.

The research consortium comes as the field of antibody research is rapidly expanding, with scientists and the drug industry looking at a slew of new conditions they might prevent or treat. Monoclonal antibodies are synthetic versions of the natural antibodies that the immune system uses to disable invading germs. These proteins are designed to bind to a single substance in the body, such as molecular fingers on the surface of tumors.

“They’re very, very specific, and they’re very, very versatile,” said Kevin Whaley, a leader of the project and the chief executive of Mapp.

Whaley and his colleagues are hoping that versatility will carry over to contraception.

The antibody they’re testing was isolated from an infertile woman and binds only to human sperm. When it’s added to sperm in the lab, the sperm quickly clump together.

“It just immobilizes them,” said Deborah Anderson, a leader of the consortium and a professor of gynecology and microbiology at BU School of Medicine. Other preliminary studies suggest that antibodies might also be able to trap sperm in the mucus in the reproductive tract.

The researchers are toying with manufacturing the antibodies inside of plants and fungi. They’ll ferry an antibody into a plant’s tissue, where the plant’s machinery will start producing the antibody. The process slowly kills the plant, which can no longer use its energy for its own tasks. After two weeks, the antibodies are harvested, ground up, purified, and turned into a dissolvable film.

“It’s like a Listerine strip,” Anderson said. A woman can place the film inside her vagina, where the film dissolves and the antibodies spread through the mucus.

The consortium is also working on a similar technology — called MB66 — that contains antibodies against the herpes simplex virus and HIV. It will soon be tested in Phase 1 trials. The researchers are hopeful that if both that product and the antibody-based contraceptive prove safe and effective, they could one day be combined into one product that can prevent pregnancy and several sexually transmitted diseases.

But that idea is a long way from being tested. For the next few years, Mapp will focus on producing the anti-sperm antibody. When it moves into a Phase 1 trial to test for safety, the researchers are also planning to look for signs that it might work to prevent pregnancy. They’ll do so with something called a post-coital test.

“We’ll administer the antibody film to women who are tubally ligated, so they’re not at risk for pregnancy,” Anderson said. Those women will then have sex with their partners. After a bit of time passes, the researchers will see whether any sperm made it past the line of defense.

There are still a number of factors up in the air — starting with whether the drug will be safe and effective.

“You have to be sure the effects don’t linger and the antibodies don’t continue to work when they’re not wanted,” said Darney, who wasn’t involved in the research. Darney noted that there have been “disappointments in antibody-based contraception in the past.”

The idea of antibody-based contraception isn’t new. From 1985 to 2000, Anderson was involved in a World Health Organization task force studying contraceptive vaccines, including one designed to immunize women with sperm. The goal: induce antibodies that would act as a contraceptive for one to three years. But the results varied wildly. Some women had weak responses that meant it wouldn’t be effective birth control, and others had strong responses that would make the vaccine hard to reverse. But Anderson said recent advances have made it possible to administer consistent doses of premade antibodies and produce a contraceptive effect that can be reversed.

The researchers still face another looming question: how much it will cost to make the antibodies, and whether it will be possible to produce enough of them.

“Antibody manufacturing platforms have evolved so that costs are dropping. Now the challenge is to meet the scale requirements,” Whaley said. The cost, in particular, is a critical point when it comes to contraception, experts said.

“Most of the people who use contraception around the world can’t pay much for it,” Darney said.

But the consortium is hopeful that continued advances in the technology — such as the plant manufacturing platforms — will make antibodies cheaper and easier to produce. That could affect more than just contraception costs.

“If we can dramatically lower cost and increase scale, that has implications for other antibody-based products,” Whaley said. “We could make these products much more accessible.”